Sensors, such as proximity sensors, are used in industrial machinery, such as welding equipment and industrial robots. Proximity sensors detect the presence of targets, such as targets formed from ferrous and non-ferrous materials. Proximity sensors are used to detect the presence of both stationary and non-stationary targets. A table for holding a work piece to be welded, such as a door panel, is an example of a stationary target. To detect a table a proximity sensor is moved toward the table until the table is detected. A moving robotic arm, such as a robotic arm moving a work piece, such as a door panel, onto a table is an example of a non-stationary target. A moving robotic arm is detected as it moves to a position near a proximity sensor.
Unfortunately, some environments in which proximity sensors are used are electromagnetically noisy environments. For example, sensors are used in environments that include arc welders. Arc welders create an alternating current or direct current environment. Some sensors fail when used in an alternating current or direct current electromagnetic field environment. A failed sensor can cause manufacturing lines to shut down or industrial machinery to malfunction. For these and other reasons there is a need for sensors that do not fail in the presence of electrical noise or an alternating current or direct current magnetic field.